The elegant Ethiopic script is another interesting story in the family tree of Proto-Sinaitic script. Ethiopic is an offshoot of the South Arabian script, as shown by similarities in the forms of the letters, and in the order of the letters. In fact, the earliest inscriptions in Ethiopia were in the South Arabian script. However, by around the 4th century CE, a new feature was developed that distinguished it from South Arabian. Vowels were "written" by adding strokes to the consonant following somewhat regular patterns. In a way, this is very similar to Brahmi-derived scripts. Some scholars have in fact proposed that Ethiopic's vowel marking system was originated from Indian influence, but it is equally likely that the system was developed in situ especially since many other Semitic scripts were already experimenting with marking vowels.

Another feature that distinguishes Ethiopic from other Proto-Sinaitic-derived scripts is that it is written from left to right rather than right to left in Hebrew and Arabic. Ethiopic originally followed the right-to-left convention of Semitic scripts, but it switched to a left-to-right direction under influence from Greek.

The Ethiopic script was used for the liturgical language Ge'ez as well as modern languages like Amharic (the official language of Ethiopia), Tigre, Tigrinya, and other languages of Ethiopia and Eritrea. The "Classic" Ethiopic script was tailored for the Ge'ez language, and so many new signs have been derived for modern languages.

The following is the basic sign inventory of the Ethiopic script as originally used for the Ge'ez language. Each sign is a syllable (consonant plus vowel), except any sign on the sixth column (ə) represents either the consonant plus the middle central vowel /ə/ or no vowel at all (in which case it is used as a pure consonant in a consonant cluster).

In addition to the basic signs, there are four series of derived signs to represent labialized velar consonants. These are velar sounds like /k/, /g/, /q/, and /h/ that are pronounced with the lips rounded regardless of the vowel.

The modern language of Amharic adapted the Classic Ethiopic script for its written form, but a few letters have been derived from existing letters to denote sounds not found in Ge'ez.